Distributor for particulate material

ABSTRACT

The present invention relates to a distributor for particulate material comprising a cylinder and a feeder screw mounted therein for conveying particulate material in the cylinder from an inlet to an outlet.

The present invention relates to a distributor for particulate materialcomprising a cylinder and a feeder screw mounted therein for conveyingparticulate material in the cylinder from an inlet to an outlet.

Distributors for particulate material such as powders, granules,granulates, flakes, fibres, and the like can be used in a number ofdifferent industrial applications. For example, it is usual in theindustrial manufacture of absorbent products, such as diapers, to addso-called superabsorbents when forming the mat of a fluffed cellulose.The term "superabsorbent" is a general name for polymer material whichhave a liquid absorbing capacity many times greater than their ownweight. Superabsorbents usually have one of the above-mentionedparticulate forms, the powder form being especially common. Theparticulate material is usually in a substantially dry state during theprocess steps which lead up to the particulate material being fed out ofthe distributor and mixed into or otherwise incorporated in an absorbentbody of, for example, fluffed cellulose. The term "substantially drystate" means in this case that no liquid has been added to theparticulate material, the only possible liquid present being thecontribution from the moisture in the surrounding air. It is undesirablethat the superabsorbent material should absorb liquid during themanufacturing state of the absorbent body, since this would impair thefunctioning of the superabsorbent material when the finished product isto be used later. It is therefore desirable that the superabsorbentmaterial be distributed in a dry state.

The distribution of dry particulate material, for examplesuperabsorbents, on a surface or in a body, involves problems. Thesurface can, for example, consist of a moving fluff web and the bodycan, for example, consist of an absorbent body of fluff fibres. In thefirst place, the distributing device for the dry particulate materialmust be suited for distributing dry material. Secondly, it is essentialthat the superabsorbent material can be advanced in a continuous flow,and that this flow can be distributed evenly either over the surface ifone wishes to make a superabsorbent coating or inside the absorbent bodyinto which one wishes to mix the superabsorbent. "Evenly" in this casedoes not mean that the entire surface of the web of material must becoated with particulate material. Rather, it is sufficient that the orthose portion(s) of the web which are coated has/have an even surfacecoating. It is of course possible to coat the entire material web withparticulate material if so desired. The same applies tothree-dimensional mixing of particulate material into the absorbentbody. It is possible that certain portions of the absorbent body cancompletely lack particulate material, but those portions of the bodywhere the particulate material is present should have a substantiallyeven distribution of particles, either in one plane inside the absorbentbody or in all dimensions of the body.

Distributors designed to produce an evenly distributed flow of particlesover a surface are previously known. EP 0 168 196 describes, forexample, a device comprising a nozzle for spreading particles conveyedin a stream of gas on to a moving porous web, providing a broad particleflow. Such a nozzle has, however, a smaller cross-sectional area at itsoutlet than at its inlet. If the nozzle is used to distribute particlesin a process step, such as mat forming processes, there is a risk thatpulp fibres will enter the nozzle via reverse suction or in anotherunintended manner. Inside the nozzle, the fibres can accumulate andthereby block the outlet of the nozzle. It is also known to distributedry particulate material by means of a screw conveyer, for example Model600 marketed by Accurate Dry Material Feeders Inc., WI, USA. From ahopper, the material is advanced by the feeder screw and out through theoutlet at the outlet end of the feeder screw, in a small string. Thisdoes not, however, provide an even transverse distribution of the feederflow; rather it provides a narrow concentrated flow.

The present invention is intended to provide a device for achieving anevenly distributed feeder flow of dry particulate material, which flowcan be used either for even particle coating of a surface or evenparticle distribution in an absorbent body.

In order to achieve this, a device of the type described by way ofintroduction is characterized in that the outlet comprises an elongatedopening in the lateral wall of the cylinder, said opening extending inthe longitudinal direction of the cylinder.

According to one embodiment of the invention, the outlet opening isinclined relative to a generatrix of the cylinder wall with the highestend of the outlet opening directed towards the inlet end of thecylinder.

According to another embodiment of the invention, the outlet openingconsists of a slot of uniform width, which can be arcuate.

According to another aspect of the invention, a plurality of elementsfor collecting and further conveyance of the distributed particulatematerial are arranged near the outlet, said elements having a collectingportion, preferably in the form of a funnel or the like, and asubsequent conveyance portion arranged in connection with the collectingportion.

According to an additional embodiment of the invention, the conveyanceportion has essentially the same cross-sectional area along its entirelength.

According to one embodiment of the invention, the conveyance portionconsists of a hose, a tube or the like, preferably with substantiallycircular cross-section.

According to another embodiment of the invention, a conveyance plate inthe form of an inclined plane is mounted in direct connection with theoutlet of the screw conveyor.

According to an additional embodiment of the invention, the elongatedoutlet opening consists of a plurality of openings arranged in series inthe longitudinal direction of the outlet.

The advantages of a distributor for particulate material according tothe present invention are numerous.

The invention can be used to create a transversely distributed particleflow which can either be applied as an even surface coating on a movingweb of material or be mixed evenly into an absorbent body. In the lattercase, the mixture can be performed evenly either in two or threedimensions.

One advantage of a device according to the invention is that the outletof the screw conveyor is relatively long so that a relatively broad flowis obtained. A broad flow makes it possible to provide an even coatingof a surface, for example a moving web of material, with particulatematerial. It is also an advantage to use a screw conveyor, since aconveyor of this type is suited to advancing in dry particulatematerial. A distributor of particulate material in accordance with thepresent invention makes it also possible to arrange conveyance lines inconnection with the broad outlet of the screw conveyor. Said conveyancelines can transport the broad outflow from the screw conveyor outlet toanother place while retaining the transverse distribution. Theadvantages of this are that the screw conveyor need not be placed in theimmediate vicinity of the narrow and difficultly accessable mat formingarea, which can consist of a mat forming drum with associated equipment.Furthermore, a plurality of flows are obtained from the conveyancetubes, which emanate from the same screw conveyor. Alternatively, thenumber of screw conveyors can be equal to the number of conveyance tubesleading to the mat forming zone, but this increases the cost of thedistributor due to the additional screw conveyors. Furthermore, thepossibilities are increased for varying the mixing ratio between theparticulate material and the cellulose fluff, by virtue of the fact thatthe outlets of the conveyance tubes can be placed at a number ofselected distances from the mat forming moulds on the mat forming drum,and in a number of different configurations relative to each other. Ifthe conveyance tubes also have the same cross-sectional area along theirentire length, including the outlet, there will be no constrictionsanywhere which could give rise to blockages due to pulp particlesaccumulated in the conveyance tubes, as in the previously known flatnozzles. The construction of the conveyance tubes is thus well adaptedto the working environment in which they are intended to operate.

The invention will be described below in more detail with reference toexamples shown in the accompanying drawings.

FIG. 1 shows in perspective view one embodiment of a device according tothe invention.

FIG. 2 shows a section along the line A--A in FIG. 1.

FIG. 3 shows a section along the line B--B in FIG. 1.

FIG. 4 shows a section along the line C--C in FIG. 1.

FIG. 5 shows in perspective a portion of a second embodiment of a deviceaccording to the invention.

FIG. 6 shows schematically the embodiment in FIG. 5 in its entirety.

FIG. 1 shows a device for distributing a dry particulate material, forexample powder, flakes, granulates, granules, fibres or the like. Thedevice is especially designed for distributing superabsorbents in one ofthe above-mentioned forms. The device comprises a hopper 1 forsuperabsorbents in powder form 2, a screw conveyor 3 for feeding thepowder 2 from the hopper 1 to a conveyance plate 4 in the form of aninclined plate for collecting and even distribution of the powder 2.Conveyance tubes for supplying the superabsorbent powder to the hopper 1are not shown in the Figure, nor is the other equipment shown which isrequired for operating the device, such as motors for driving the screwconveyor.

The powder when conveyed is substantially dry, i.e. in addition to theeffect of the surrounding ambient humidity, there is no added moisture.Feeding moist powder or other solid particulate material by means of thescrew conveyor is quite difficult and other methods and devices must inthat case be used to obtain a satisfactory result.

The screw conveyor is arranged inside the cylinder 5, which has an inlet6 at its end adjacent the hopper 1 and an outlet 7 which is elongatedand consists of a slot 8 in the lateral surface of the cylinder in thelongitudinal direction thereof. As shown in FIG. 1, the cylinder can befixedly mounted to the hopper. The slot 8, which is arcuate, extendsfrom a highest position at the slot end 9 closest to the inlet 6, to alowest position at the other distal end 10 of the slot. The latterdistal end 10 is disposed near the distal end 11 of the cylinder 5, i.e.the end farthest away from the hopper 1. The distal end 11 of thecylinder is completely encapsulated so that no powder can be fed outthat way.

The arcuate shape of the slot 8 is adapted to the conveyance propertiesof the powder, i.e. its capacity to flow. The slot 8 is not necessarilyarcuate; it can also be straight. The incline of the slot is dependenton the length of the outlet 7, which is in turn dependent on the desiredtransversed distribution or extent of the outflow.

The threads 12 of the feeder screw are indicated by dashed lines insidethe cylinder 5. When the screw 3 rotates, the superabsorbent powder 2will be advanced towards the outlet 7 by the threads 12 inside thecylinder 5, whereafter the powder 2 will be successively fed out throughthe slot 8 in a number of vertical flows 13 spaced along the entirelength of the slot.

The powder flows shown in FIG. 1 are to be regarded as a simplifiedmomentary picture of the actual distributing process where the flows aremore diffuse in shape. The flows move along the outlet 7 as the screw 3rotates so as to obtain an even distribution of discharged materialalong the cylinder 5.

The powder flows 13 fall down onto the inclined plate 4, where they aremixed with each other and fall down as an even powder curtain 16 onto aweb 14 of material, which is moving in the direction of the arrow.

In this manner, one has achieved by means of the screw conveyor an evenparticle coating of a surface of the moving material web. In the exampleshown, the particle coating is continuous in a central strip of thematerial web, but according to another process described in a co-pendingpatent application, a masking web inserted between the inclined plate 4and the material web 14 makes it possible to obtain pre-determineddiscrete particle-coated areas on the material web 14.

FIGS. 2-4 show a section through the cylinder 5 along the lines A--A,B--B and C--C, respectively, in FIG. 1, and how the superabsorbentpowder 2 is successively fed out through the slot 8.

The feeder screw itself is symbolized in the FIGS. 2-4 by a round ring.

FIG. 2 shows how the powder 2 is advanced in the cylinder 5 at a stagebefore it has reached the slot 8. In FIG. 3, the feeder screw 3 hasadvanced the powder 2 approximately half of the length of the slot, andabout half of the particles have already been fed out into the powderflow 14. FIG. 4 shows how the distribution has almost reached the distalend 10 of the slot 8 and thereby its lowest position, whereupon the lastparticles 2 are fed out through the slot 8.

The distal end 10 of the slot 8 is placed in the example shown at thelowest point of the cylinder. This ensures that all of the particulatematerial conveyed by the feeder screw will be fed out of the cylinderthrough the slot 8 and this prevents particulate material from beingcollected at the outlet end 11 of the cylinder in the space below thelowest end of the slot, which would otherwise disturb the evendistribution of the flow of particles fed from the slot.

A second embodiment of the invention is shown in FIGS. 5 and 6. Insteadof allowing the particles to fall down and coat a surface of a materialweb, for example, as in FIG. 1, four collecting and conveyance elements15 are arranged under the inclined plate 4. These elements 15 have acollecting portion 17, for example a funnel, and a subsequent conveyanceportion 18 arranged in connection with the collecting portion 17. FIG. 5shows how the powder curtain 16 falls down into the collecting portions17.

FIG. 6 shows schematically a device in its entirety and how theconveyance portions 18 lead to a mat forming zone 19 on a machine, forexample for manufacturing diapers. In order to facilitate the conveyanceof the superabsorbent powder in the conveyance portions 18, which arefor example hoses, tubes or the like, an ejector 20 is arranged betweenthe collecting portion 17 and the conveyance portion 18.

By arranging the openings 21 of the conveyance portions 18 at suitablelocations within the mat forming zone 19, it is possible to obtain theeven distribution in the absorbent body which is desired. A spreading ofthe openings 21 vertically relative to the mat forming zone provides anessentially even three-dimensional distribution of the superabsorbentpowder in the absorbent body formed, while a concentration of theopenings 21 in the mediate vicinity of the mat forming moulds (notshown) provides an even layer application within the absorbent body.

The conveyance portions are constructed so that they have essentiallythe same cross-sectional area along their entire length. Thecross-section is preferably circular, but the most essential feature isthat there will be no constrictions.

FIG. 6 also shows schematically an inlet 22 for the superabsorbentpowder which comes from a magazine (not shown). A vacuum pump 23 conveysthe powder through the feed line 22 to the hopper 1.

The invention is not intended to be limited to the examples shown.Rather, a number of modifications are possible within the scope of thepatent claims.

It is, for example, possible to eliminate the inclined plate in thosecases where the particulate material is to be further conveyed by meansof the collecting and conveyance elements, as shown in FIGS. 5 and 6. Itis also conceivable that the outlet of the screw conveyor can be dividedinto a longitudinal row of small slots, which are separate from eachother by remaining portions of the lateral wall of the cylinder. Such adesign can have advantages as regards strength, and the remainingportions between the slots can suitably be placed within the areas ofthe thread crests of the feeder screw.

It is also conceivable that another dry particulate material thansuperabsorbent powder can be fed by means of a distributor according tothe present invention.

I claim:
 1. A distributor for particulate material, comprising:anonrotating hollow cylinder having an inlet and an outlet therein, saidinlet being located at a first end of said cylinder, said cylinderhaving a closed second end, means for supplying particulate material tosaid inlet, said means for supplying being fixedly mounted to saidnonrotating hollow cylinder, a feeder screw disposed in said cylinderfor conveying particulate material in the cylinder from said inletsolely to said outlet, and drive means for rotating the feeder screw inthe cylinder, said outlet comprising an elongated opening in a lateralwall of the cylinder, said outlet opening extends in a longitudinaldirection of the cylinder and is inclined relative to a generatrix of acylinder wall with a highest end of the outlet opening directed towardssaid first end of the cylinder, whereby the particulate material isdistributed through the outlet in a plurality of vertical flows spacedalong the outlet and moving along the outlet as the feeder screw rotatesso as to obtain an even distribution of discharged material along thecylinder.
 2. The distributor according to claim 1, wherein a lowest endof the outlet opening is located in the vicinity of the outlet end ofthe cylinder and substantially in a lowest portion of the cylinder wall.3. The distributor according to claim 1, wherein the outlet openingconsists of a through-slot of uniform width in the wall of the cylinder.4. The distributor according to claim 3, wherein the slot is arcuate. 5.The distributor according to claim 4, wherein the outlet openingincludes a plurality of openings arranged in series in the longitudinaldirection of the cylinder.
 6. The distributor according to claim 3,wherein the width of the slot varies.
 7. The distributor according toclaim 3, wherein the outlet opening includes a plurality of openingsarranged in series in the longitudinal direction of the cylinder.
 8. Thedistributor according to claim 3, further including a plurality ofelements for collecting and further conveyance of the distributedparticulate material arranged near the outlet, said elements having acollecting portion, and a subsequent conveyance portion arranged inconnection with the collecting portion.
 9. The distributor according toclaim 3, further comprising a conveyance plate, in the form of aninclined plane, mounted in direct connection with the outlet.
 10. Thedistributor according to claim 1, wherein the outlet opening includes aplurality of openings arranged in series in the longitudinal directionof the cylinder.
 11. The distributor according to claim 10, furtherincluding a plurality of elements for collecting and further conveyanceof the distributed particulate material arranged near the outlet, saidelements having a collecting portion, and a subsequent conveyanceportion arranged in connection with the collecting portion.
 12. Thedistributor according to claim 1, further including a plurality ofelements for collecting and further conveyance of the distributedparticulate material which are arranged near the outlet, said elementshaving a collecting portion, and a subsequent conveyance portionarranged in connection with the collecting portion.
 13. The distributoraccording to claim 12, wherein the conveyance portion has essentially asame cross-sectional area along an entire length of the conveyanceportion.
 14. The distributor according to claim 13, wherein theconveyance portion includes a hose.
 15. The distributor of claim 14,wherein the hose has a substantially circular cross-section.
 16. Thedistributor according to claim 12, further comprising ejectors coupledto inlet portions of the conveyance portions.
 17. The distributoraccording to claim 16, further comprising a conveyance plate, in theform of an inclined plane, mounted in direct connection with the outlet.18. The distributor of claim 12, wherein the collecting portion is inthe form of a funnel.
 19. The distributor according to claim 12, furthercomprising a conveyance plate, in the form of an inclined plane, mountedin direct connection with the outlet.
 20. The distributor according toclaim 1, further comprising a conveyance plate in the form of aninclined plane, which is mounted in direct connection with the outlet.21. A distributor for particulate material, comprising:a nonrotatinghollow cylinder having an inlet and an outlet therein, said inlet beinglocated at a first end of said cylinder, said cylinder having a closedsecond end, means for supplying particulate material to said inlet, saidmeans for supplying being fixedly mounted to said nonrotating hollowcylinder, a feeder screw disposed in said cylinder for conveyingparticulate material in the cylinder from said inlet solely to saidoutlet, drive means for rotating the feeder screw in the cylinder, saidoutlet comprising an elongated opening in a lateral wall of thecylinder, said outlet opening extends in a longitudinal direction of thecylinder and is inclined relative to a generatrix of a cylinder wallwith a highest end of the outlet opening directed towards said first endof the cylinder, whereby the particulate material is distributed throughthe outlet in a plurality of vertical flows spaced along the outlet andmoving along the outlet as the feeder screw rotates so as to obtain aneven distribution of discharged material along the cylinder, and aconveyance plate, forming an inclined plane and mounted directlyadjacent and below said outlet opening.
 22. The distributor according toclaim 21, wherein said conveyance plate has an upper edge extendingtransverse to an inclination of said inclined plane, said upper edgefurther extending along the longitudinal direction of the cylinder adistance at least equal to an extension along the longitudinal directionof the cylinder of said elongated opening.
 23. The distributor accordingto claim 22, wherein said cylinder has a substantially horizontalcentral axis.
 24. The distributor according to claim 21, wherein saidcylinder has a substantially horizontal central axis.